Commit 178bf2b9 authored by Pavel Tatashin's avatar Pavel Tatashin Committed by David S. Miller
Browse files

sparc64: optimize loads in clock_sched() 



In clock sched we now have three loads:
	- Function pointer
	- quotient for multiplication
	- offset

However, it is possible to improve performance substantially, by
guaranteeing that all three loads are from the same cacheline.

By moving these three values first in sparc64_tick_ops, and by having
tick_operations 64-byte aligned we guarantee this.

Signed-off-by: default avatarPavel Tatashin <pasha.tatashin@oracle.com>
Reviewed-by: default avatarShannon Nelson <shannon.nelson@oracle.com>
Reviewed-by: default avatarSteven Sistare <steven.sistare@oracle.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent b5dd4d80

arch/sparc/include/asm/timer_64.h

+5 −0
Original line number Diff line number Diff line
@@ -9,7 +9,12 @@ 
#include <linux/types.h>

#include <linux/init.h>



/* The most frequently accessed fields should be first,

 * to fit into the same cacheline.

 */

struct sparc64_tick_ops {

	unsigned long ticks_per_nsec_quotient;

	unsigned long offset;

	unsigned long long (*get_tick)(void);

	int (*add_compare)(unsigned long);

	unsigned long softint_mask;

arch/sparc/kernel/time_64.c

+7 −10
Original line number Diff line number Diff line
@@ -164,7 +164,7 @@ static unsigned long tick_add_tick(unsigned long adj) 
	return new_tick;

}



static struct sparc64_tick_ops tick_operations __read_mostly = {

static struct sparc64_tick_ops tick_operations __cacheline_aligned = {

	.name		=	"tick",

	.init_tick	=	tick_init_tick,

	.disable_irq	=	tick_disable_irq,
@@ -391,9 +391,6 @@ static struct sparc64_tick_ops hbtick_operations __read_mostly = { 
	.softint_mask	=	1UL << 0,

};



static unsigned long timer_ticks_per_nsec_quotient __read_mostly;

static unsigned long timer_offset __read_mostly;



unsigned long cmos_regs;

EXPORT_SYMBOL(cmos_regs);
@@ -784,11 +781,11 @@ void __init time_init(void) 


	tb_ticks_per_usec = freq / USEC_PER_SEC;



	timer_ticks_per_nsec_quotient =

	tick_operations.ticks_per_nsec_quotient =

		clocksource_hz2mult(freq, SPARC64_NSEC_PER_CYC_SHIFT);



	timer_offset = (tick_operations.get_tick()

			* timer_ticks_per_nsec_quotient)

	tick_operations.offset = (tick_operations.get_tick()

			* tick_operations.ticks_per_nsec_quotient)

			>> SPARC64_NSEC_PER_CYC_SHIFT;



	clocksource_tick.name = tick_operations.name;
@@ -816,11 +813,11 @@ void __init time_init(void) 


unsigned long long sched_clock(void)

{

	unsigned long quotient = tick_operations.ticks_per_nsec_quotient;

	unsigned long offset = tick_operations.offset;

	unsigned long ticks = tick_operations.get_tick();



	return ((ticks * timer_ticks_per_nsec_quotient)

		>> SPARC64_NSEC_PER_CYC_SHIFT)

		- timer_offset;

	return ((ticks * quotient) >> SPARC64_NSEC_PER_CYC_SHIFT) - offset;

}



int read_current_timer(unsigned long *timer_val)

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